How to create a basic slide show

The first step, needless to say, is to first fetch the
images you want to include in the slideshow. For this tutorial, we'll be
using these three images:

"firstcar.gif"

"secondcar.gif"

"thirdcar.gif"

Imagine yourself as a car salesmen, and these three cars are
the ones you are selling!

Step 2: Preload the images using JavaScript.

The term "preload" in JavaScript refers to the loading of
images into cache prior to displaying them. Preloading images is "necessary"
in a slide show, since the switching between images have to be
instantaneous, without any delay:

We've created three instances of the image object and stored
them inside a JavaScript Array, each
referring to one of the images that make up the slide show. By doing so, the
images are loaded into cache, standing by for us to display at anytime.
Notice that the entire code is inserted in the <head> section of the page
(Detailed discussion of preloading images can be found
here).

Step 3: Add in the html codes necessary to
display the first image of the slide show.

All we've done above is insert the first image of the slide
show using HTML. Notice how we gave the image a "ID" attribute. By naming
the image with an arbitrary ID value, it enables JavaScript to access and
manipulate the image, which we will see next.

Step 4: With everything in place, all we need now
is a script that accesses the above image and changes the src of the image
periodically, creating a slide show. The below lists the complete script:

The left hand side of the equal sign ("=") accesses the
image container we've inserted onto the page, by using the JavaScript method
document.getElementById() to access the image by, well, its ID
attribute value. After that, we reference its "src" property,
which is what lets us change the image's src property to another image URL
or path. The right hand side dynamically assigns a new src (path) to the image
from one of the image paths stored inside our JavaScript image array, thus changing
the image. The three possible paths the image may now receive are:

in that order. Elements within a JavaScript Array are
referenced based on their index position within the Array, starting at 0 for
the first element, 1 for the second etc.

Step 5: Putting it all together.

We've preloaded the images, inserted the first image of the
slideshow, and created the function necessary to change the path associated
with the image every few seconds. All we have to do now is put it all together into one page,
and we've got ourselves a slideshow: